Coagulation is the initial make-or-break unit process in water-pollutant separation systems. Flocculation immediately follows coagulation. Combined, coagulation-flocculation represents pretreatment processing for the formation of floc (˜mm size aggregates that incorporate pollutants) for their subsequent physical separation. Separation of floc-pollutants is accomplished by a large-scale separation process such as drinking water filtration (using granular-media), membranes and/or desalting pretreatment, wastewater treatment, fats-oil-grease removal from industrial wastewater, waste metal and trace element removal, and dewatering including paper making and sludge dewatering. Coagulant dosage control and flocculation mixing control (to a lesser extent) are the two levers that plant operators have for controlling the entire coagulation-flocculation-clarification filtration process.
Coagulation involves chemical addition and dispersion to process water. Coagulation is powerful. It can induce >10,000-fold pollutant-particle size changes, and >1,000,000-fold reduction in number concentration of infectious organisms such as the amoeba Cryptosporidium. Coagulation is versatile. It can induce removal of a diverse variety of pollutant species including:                (i) Ions of arsenic, phosphorus, fluorine, and trace metals;        (ii) Dissolved organics that may form carcinogens;        (iii) Algae, dead microorganisms, cellular detritus:        (iv) Infectious viruses, bacteria, and amoeba; and        (v) Particulate matter harboring other pollutants.        
The successful application of coagulation represents a challenge because coagulation-flocculation effects are manifold, slow to manifest, varied, and used in a wide range of applications. Coagulation-flocculation pretreatment represents the ‘big lever’ for the plant operators for controlling pollutant-removal performance both quality and quantity (throughput).
Coagulation is instantaneous whereas flocculation nominally requires from minutes (for dense slurries) to hours (for dilute suspensions in older facilities). Nominally, coagulation converts, otherwise stable, negatively charged pollutant species into neutral ‘sticky’ bodies that gradually grow in size as a result of particle-particle collisions caused by Brownian motion and mild turbulent fluid mixing. A fundamental requirement of coagulant dosing is that the total negative charged demand of water must be met by the positive-charge supplied by the coagulant chemicals, referred to as charge neutral coagulation. Dosing beyond this point can be more costly or counterproductive. Flocculation results in the aggregation of pollutant-coagulant sub-particles into larger and more easily removable entities, or floc particles. Particle size depends upon the nature of the mixing regime and floc strength characteristics for a given raw water quality and coagulation chemistry. Mixing intensity control represents the physical means for manipulating floc particle characteristics, for a given coagulation-chemistry regime.
Because the terms coagulation and flocculation are used interchangeably by some, these and related terms require defining as to their meaning as used in this invention disclosure. Coagulation refers to the action of the addition of chemical species that in turn lead to the instantaneous precipitation, adsorption, and destabilization of dissolved and particulate matter. Flocculation refers to the agglomeration or aggregation of the destabilized colloids and precipitates. Coagulation-flocculation refers to the coupled unit processes as a pretreatment system preceding the pollutant-floc separation step(s).
Prior art (manual) jar tests, used since at least the 1920s, measure turbidity (water cloudiness) after the coagulant addition, flocculation mixing, and settling. No quantitative analysis is made of the visible floc particles. No data about the sample is collected until test completion after settling. Systems and methods that gather more, better and faster information about the coagulation effects, flocculation progress, and gravitational settling processes are desired. Documentation and analysis of these dynamic information rich systems and methods would enhance water and wastewater treatment plant operation.
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